Vibrator for, and method of compacting concrete and similar masses

ABSTRACT

A vibrator for, and a method for, compacting concrete and the like material in which the vibrator has a housing and an eccentric mass therein, a fluid supply leads into the chamber in which the mass is located for actuating the mass by fluid pressure and an exhaust leads from the chamber. The rate of supply of fluid to the chamber is regulated by a control sensitive to the amplitude of movement of the eccentric mass so that when the vibrator is engaged with the material to be compacted there is maximum fluid flow to the chamber and when the vibrator is disengaged from the material, the supply of fluid to the chamber is reduced.

United States Patent 1191 Seidl et al. I

1451 Apr. 17, 1973 VIBRATOR FOR, AND METHOD OF COMPACTING CONCRETE AND SIMILAR MASSES Primary Exah1iner-Robert W. Jenkins Assistant ExaminerAlan I. Cantor Attorney-Walter Becker l [75] Inventors: Franc Seidl; Philipp Uebel, both of Munich, Germany 57] ABSTRACT ['73] A Ass'gnee: wacker werke Mumch A vibrator for, and a method for, compacting concrete many 7 andthe like material in which the vibrator has a hous- 22 Filed; Oct 13, 1971 ing and an eccentric mass therein, a fluid supply leads into the chamber in which the mass is located for ac- PP 188,905 tuating the mass by fluid pressure and an exhaust leads I from the chamber. The rate of supply of fluid to the v chamber is regulated by a control sensitive to the am- [301' Foreign Application nty Data plitude of movement of the eccentric mass so that 0m. 14, 1970 Germany ..1 20 50 364.4 when thevibrator is engaged with the material to be 1 compacted there is maximum fluid flow to the 52 useci. .;2s9/ 1 R, 259/1310. 43 ehember end when the vibrator is disengaged from the 51 Int Cl. ..B01f 11/00 material" Supply of fluid the chamber is [58 Field of Search .259/010. 42, DIG. 43,

' 259/DIG. 44, l R

[56] References Cited 25 Claims, 6 Drawing Figures UNITED STATES PATENTS 2,520,044 8/1950 Mason ..259/DIG. 43

PRESSURE MEDIUM v i I a 5 a i 7 17 I I i: t

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PATENTEI] APR 1 7 I975 SHEET 1 OF 3 PRESSURE MEDIUM FIG -2 PRESSURE MEEiIUM a a m w v 7 M V 7 w/ t 7 9L d M 8 IT/ /g x A, Z v w y P m 6 9 5 3 4 mm P PATENTEDAPR 1 11915 3.127. 890

SHEET 2 BF 3 PRESSURE MEDIUM PRESSURE meoui'nf Y FIG-4 2a a 24 y 7 4o" VIBRATOR FOR, AND METHOD OF COMPACTING CONCRETE AND SIMIDAR MASSES The present invention relates to a vibrator for and method of compacting concrete or similar masses, according to which an eccentric mass is acted upon by a pressure medium, for instance, air, and rotated so as to roll in the housing of the vibrator.

With heretofore known methods of the above mentioned type, the media to be compacted by means of the vibrator are compacted by supplying a constant quantity of pressure medium. As a result thereof, when the vibrator is idling, in other words, when it is not in contact with the medium to be compacted, the speed of the eccentric mass increases considerably and reaches very high values because the supplied quantity of pressure medium is calculated in conformity with the quantity of pressure medium required for the speed when the vibrator works under load, and it will be appreciated that in order to obtain this speed, a relatively high quantity of pressure medium is necessary in view of the fact that the air resistance of the eccentric grows considerably when the vibrator works under load. The high idling speed which results from the fact that regardless of the load, the consumption of the supply of the pressure medium always remains substantially the same, brings about an undue surface pressure and thereby an over-stress of the materials so that the individual parts of the vibrator wear unduly fast. The high circumferential speeds of the eccentric mass furthermore results in a considerable noise development which far exceeds the decibel number for the human ear desired for reasons of health. v

Therefore, it has been suggested to throttle the pressure medium by means of a control handle in conformity with the judgement of the operator, which judgement depends on the ear of the operator. Such an arrangement, however, has the drawback that the operator must keep one hand continuously on the control handle in order to adjust the speed in conformity with the respective requirements. This means that the operator cannot fully concentrate his mind on the compacting operation so that a faulty compacting may occur and even a de-mixture of the material to be compacted. Aside therefrom, the employment of the method with a constant supply of pressure medium, is also limited because the control handle for controlling the speed is arranged approximately two meters behind the vibration body on the protective hose so that such vibrators cannot be employed for instance, for the compacting of posts unless first an awkward disassembly and extension of the protective hose is effected.

In view of the usual great noise on building sites, the operator will as a rule not be able to determine the respective speed of the eccentric mass by ear that a proper adaptation will be possible, particularly if, for instance, an inner vibrator is to be immersed into the material to be compacted. Y

It is, therefore, an object of the present invention to provide a vibrator for and method of compacting concrete, which will overcomethe above mentioned drawbacks and will permit the operator to concentrate his mind fully upon the compacting operation so that independently of the judgment of the operator, the ecology will be properly taken into consideration, which means that undue environmental noise development will be prevented, while on the other hand, the consumption of pressure medium will be reduced over that employed with heretofore known vibrators.

" These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIGS. 1 to 5 respectively illustrate five different embodiments of the present invention.

FIG. 6 is an enlargement of the central portion of FIG. 5.

The vibrator and method according to the present invention is characterized primarily in that the quantity of the pressure medium supplied to the eccentric mass for actuating the same is automatically so controlled that the speed of the eccentric mass during the idling of the vibrator will not materially exceed the speed calculated for the vibrator working under load.

The method according to the invention may be carried out in such a way that the quantity of the pressure medium is so controlled that the speed of the eccentric mass remains substantially constant when the vibrator works under load. In this instance, the quantity of pressure medium supplied to the eccentric mass adapts itself precisely to the compacting power required by the vibrator.

The control of the supply of pressure medium for the idling operation of the vibrator may be effected so that the idling speed of the eccentric mass remains either approximately at the value provided for the vibrator when working under load, or may even drop below this value, which is particularly advantageous with regard to ecology.

The method according to the invention may be practiced principally also by heretofore known vibrators. In such an instance, it is merely necessary to measure the speed of the eccentric mass for instance, by electronic means, and to control the supply of pressure medium to the eccentric mass in conformity with the thus measured speed. This may easily be effected outside the vibrator. However, it is considerably simpler and less expensive to practice the method according to the invention by providing the vibrator itself with means which will effect the control in conformity with the present invention. Thus, a vibrator according to the present invention may be characterized in that the path on which the eccentric mass rolls in the housing of the vibrator is so designed that the circulating eccentric mass exerts a controlling or adjusting force upon a control element which in the vibrator housing is adjustable against a constant and stroke-dependent variable counter force preferably in the direction of the axis of rotation of the eccentric mass and controls the supply of the pressure medium to said eccentric mass.

The characteristics of the adjusting force and the counter force determine the speed behavior of the eccentric mass during the idling of the vibrator and when the vibrator works under load, and are to be selected in conformity with the requirement of the method of the invention. As eccentric masses, preferably a ball may be used.

According to a first embodiment of a vibrator according to the present invention, the rolling path of the eccentric mass is formed by a part fixedly connected to the vibrator housing and movable relative thereto under the pressure exerted by the eccentric mass onto its rolling path of track against the counter force, said movable part actuating a control element. The movable part of the rolling path is preferably designed in a truncated cone-shaped manner. The rolling path along which the eccentric mass rolls may be formed by a sleeve which is displaceable in the direction of the axis of rotation of the eccentric mass in the vibrator housing against the counter force. This sleeve is adapted to act as valve or sliding element for varying the cross section of the flow passage through which the pressure medium passes toward the eccentric mass.

According to a structurally particularly simple embodiment of a vibrator according to the present invention, the rolling path for the eccentric mass, which acts counter to the counter force, may be tapered and may be arranged stationarily in the vibrator housing. In this instance, the eccentric mass is adapted to press against a piston acted upon by the oncoming pressure medium, while the control element is connected to the said piston. The stationary rolling path is preferably conical. A dropping of the idling speed below the value selected for the vibrator working under load or a drop in the range of values may with this embodiment be realized by having the conical rolling path for the eccentric mass comprise sections of different inclination or the piston acted upon by the pressure of the supplied pressure medium is designed as a differential piston which generates a counter force that changes suddenly and instantaneously with constant pressure supply in conformity with the displacement stroke of the eccentric. The last mentioned two steps may, if desired, also be applied simultaneously.

While according to the above mentioned embodiments, the control mass is formed by the eccentric itself, it is also possible according to a further development of this invention to have the control mass formed by a control body which is separate from the eccentric mass and is located in the vibrator housing. With a vibrator of this last mentioned type, the eccentric mass merely has to carry out the function of an oscillation generator in the vibrator housing as is customary with heretofore known inner vibrators, so that when designing the last mentioned vibrator according to the invention in connection with the rolling path without compromise, attention has to be paid only to what is important for the realization of an optimum oscillation generation, including a rolling of the eccentric at as low a rolling resistance as possible and as high a rolling path diameter as possible with a given vibrator outer diameter. On the other hand, in view of the separation of the eccentric mass from the control mass, it is, for the construction of said control mass and of the pertaining control elements, merely necessary without considering the main function of the eccentric mass, to concentrate on a high safety of operation and as simple a structural design as possible, and on a long life span of the device.

According to a further development of the present invention, there is suggested a structurally particularly simple, reliable and control -wise sensitive construction of a control element with a control mass separated from the eccentric mass. The main feature of this construction consists in that the control body is so arranged in the vibrator that its distance from the axis of rotation of the eccentric masses is variable under the influence of mass forces occurring during the vibration. The control body is, preferably, against the action of the mass forces decisive for change of its distance from the axis of rotation of the eccentric masses, held by means of a predetermined counter force in a rest position closer to said axis, from which rest position it jumps out when the mass forces exceed the counter force, and to which rest position it automatically returns when the mass forces drop below a certain value. This jumping out of the control body from its rest position or position of detention and its return to said position are taken advantage of for the direct or indirect control of the effective cross section of the pressure medium supply passage leading to the eccentric mass.

With the above mentioned control member, the control body preferably directly controls the cross section of a pressure medium passage, the magnitude of which is decisive for the variable effective cross section of the pressure medium passage to the eccentric mass. This pressure medium passage may be formed by the pressure medium supply passage to the eccentric mass itself, which would correspond to a direct control by the control body, however, also on indirect control of the last mentioned passage may be provided. To this end, according to a further development of the invention, it is suggested to employ the pressure medium passage controlled by the control body as auxiliary passage in a control piston which controls the effective cross section of the pressure medium supply passage to the eccentric mass and which interconnects both end faces of said control piston. One end face is acted upon continuously by the preferably not yet controlled connecting pressure or a pressure derived therefrom of the pressure medium conveyed to the eccentric mass, whereas the other end face of the control piston is acted upon by variable counter forces which, with inherent displacement of the control piston, and in open position of the pressure medium passage controlled by the control body, has a different magnitude than in the closing position of said control piston.

The counter force acting upon the control piston is preferably formed by a spring load and by the pressure of the pressure medium in a pressure medium chamber arranged in front of the pertaining end face of the control piston. Said pressure medium chamber communicates through a narrow throttling area with the flowoff passage behind the eccentric mass.

It is also advantageous to arrange the control piston symmetrically with regard to the axis of rotation of the eccentric mass and movable in the vibrator housing in the direction of said mass while the pressure medium passage which interconnects the end faces of the control piston, may be so arranged that it extends centrally through said pressure medium passage. In the control piston, there should furthermore be provided a hollow chamber which receives the control mass in the form of a ball. Furthermore, said control mass should be held in its rest position or position of detention under the pressure acting upon the on-flowing side of the control piston at the mouth which faces the hollow control piston chamber and pertains to the pressure medium passage of circular cross section, which pressure medium passage is controlled by said onflowing side of the control piston.

The rolling path for the eccentric mass in the interior of the vibrator housing is, for purposes of encountering a main air resistance, preferably so designed that said eccentric mass rolls on said rolling path under line contact.

' Referring now to the drawings in detail and FIG. 1 thereof in particular, it will be seen that in housing 1 of the vibrator, an eccentric mass 2 rolls on a rolling path which is formed by two truncated cone-shaped path sections 4 and 5. The path section 5 is provided on a sleeve 6 which is movably arranged in housing I. Sleeve 6 has a control edge 9 and rests against a fixed portion of housing 1 by means of elastic elements, which, in the specific instance shown, are formed by dish springs 7 The movable control edge 9 cooperates with a control edge 11 of the vibrator which control edge 11 is either formed by or forms a part fixedly connected to the housing. The supply of pressure medium is effected through a feed line 8 and a flow passage 10. This vibrator operates in the following manner:

The pressure medium, for instance, air, passes through the feed line 8 into the flow passage 10. In the flow passage 10 there are located the stationary control edge 11 and the movable control edge 9 located opposite said stationary control edge 11 and arranged on the displaceable sleeve 6 The pressure medium passes between the two control edges 9 and 11 and tangentially acts upon the eccentric mass 2 which rolls between the rolling path sections 4 and 5 forming the rolling surfaces to be engaged by the eccentric mass 2.

In view of the fact that the eccentric mass is acted upon by the pressure medium, it rotates in the housing at a certain speed of rotation. The higher the speed of the eccentric mass 2, the greater will bethe generated centrifugal force, and the greater will also be the pressing force exerted upon the rolling path section 5. On the other hand, the resistance of the eccentric mass 2 encountered on the rolling path 4, 5 depends on the degree to which the medium for instance, concrete, which is in contact with the vibrator housing 1, is compacted. The running resistance is low when the vibrator is located outside of the medium to be compacted, and the running resistance increases considerably when the vibrator engages the medium to be compacted for instance, is immersed therein, in which instance the eccentric mass has the tendency to reduce its speed.

If the force exerted by the eccentric mass upon the rolling path section 5 with the tendency to increase the speed becomes greater than the spring force exerted by the elastic elements 7 upon the sleeve 6, the rolling path section 5 is pressed away from the rolling path section 4 by the eccentric mass 2., In this way, the control edge 9 is moved toward the control edge 11 so that the cross section of the flow passage 10 will be narrowed. In view of the narrowing of the cross section, less pressure medium can flow through to act upon the eccentric mass 2. The control strokes and control forces are so selected that the frequency of the eccentric mass remains constant.

When the spring force generated by the elastic elements with a tendency to decrease the speed becomes greater than the force at which the eccentric mass 2 presses against the rolling path section 5, the movable sleeve 6 is moved toward the eccentric mass 2 whereby the cross section of the flow passage 10 is increased. As a result thereof, a greater quantity of pressure medium can pass through per time unit and can act upon the eccentric mass 2. The frequency remains therefore again constant.

With the embodiment according to FIG. 2, in the vibrator housing 1, there is provided a truncated coneshaped stationary rolling path 4 for the eccentric mass 2'. The inclination of the rolling path 4 brings about that the ball 2' which forms the eccentric mass will exert an adjusting force which, when viewing FIG. 2, is directed toward the upper side and which is exerted upon a piston 20 centrally adjustably located in the vibrator. This piston 20 forms on that side thereof which faces away from the ball 2 a valve body 21.

Valve body 21 cooperates with a stationary valve seat 22 through which the pressure medium flows to the ball 2. From the control valve comprising the valve body 21 and the valve seat 22, the pressure medium passes through flow passages 23 and'24 to ball 2' and tangentially acts upon said ball 2' and rotates the same.

The valve body 21 and piston 20 are continuously exposed to the pressure of the oncoming pressure medium, which pressure medium has the tendency to displace said body 21 and piston 20 in the direction toward the ball. Thus, the piston 20 exerts upon the ball 2' a counter force acting counter to the upwardly directed adjusting force. Inasmuch as the adjusting force of the ball 2' caused by the inclination of the rolling path 4 depends on the speed of said ball, also the degree of the throttling of the pressure medium flow at the valve 211, 22 represents a factor which is dependent on the speed of the ball. The parts which are decisive for the generation of the adjusting force and the counter force are so dimensioned that the speed of the ball 2' in idling condition of the vibrator and under the load of the vibrator are, by a corresponding control of the pressure medium supply in the valve 21, 22, approximately constant. v

The embodiment of FIG. 3 differs from that of FIG. 2 primarily in that the stationary rolling path 4" has two sections 4a" and 4b of a different inclination. The right-hand section 4b", which is closer to the valve 21, 22, has the greater inclination. This brings about that the adjusting force of ball 2' after exceeding a maximum speed of the ball obtained when the vibrator changes its phase of operation to idling, instantaneously and suddenly changes to a higher value so that subsequently the valve brings about a very high degree of throttling of the pressure medium supply whereupon the speed of rotation of the ball drops to a value that is lower than the value provided for the vibrator operating under load. When subsequently the vibrator is again placed under load, the speed, starting from the above described low value, first drops further whereby the piston 20 will be able to push back the ball into the section 40" while simultaneously valve 21, 22 opens so that thereupon the speed of rotation of the ball due to the increased supply of pressure medium again increases to the higher value provided for the vibrator working under load. The speed of rotation of the ball is held approximately constant at this higher value by the alternate action between the adjusting force of ball 2 and the counter force of piston 20 and the inherent control of the pressure medium supply.

FIG. 4 shows still another embodiment of the invention according to which the control element serving for producing the counter force also serves for controlling the pressure medium supply to the eccentric mass-balls 2 or 2' for a vibrator according to FIG. 2 or FIG. 3. To this end, FIG. 4 is provided with a differential piston which has its right end face (with regard to FIG. 4) acted upon by pressure of the oncoming pressure medium and as a control piston controls the flow of the pressure medium into a flow passage 24 from which the pressure medium in a non-illustrated manner passes to the ball 2 or 2' which are tangentially acted upon by the pressure medium and are thus rotated. A by-pass passage 25 is so provided that the pressure medium chambers on the upper side of the differential piston and of the oppositely located lower end face,which has a smaller effective cross section are in communication with each other when the flow control cross section controlled by piston 20'to the flow passage 24 is small, and that this connection is interrupted when the differential piston 20' in a further lower position frees a greater cross section. In the first mentioned instance, the counter force generated by the differential piston 20' and conveyed by piston rod 26 upon the ball 2 or 2' has a low value which after closing the connection 25 changes instantaneously to a higher value. The operation of a vibrator equipped with a control member of FIG. 4 and otherwise designed in conformity with FIG. 2 or FIG. 3 is the same as described above in connection with FIG. 3 because the instantaneous reduction in the counter force during the displacement of the differential piston from left to right, in other words, when passing from the operational phase under load to the operational phase of idling, has the same effect as the instantaneous increase in the adjusting force which at this time is obtained with the design of the vibrator according to FIG. 3.

A narrow throttling passage 27 prevents that, following the closing of the connection 25, the pressure medium on the left-hand side of differential piston 20 will form a pressure cushion which would affect the control movement of the differential piston 20'.

Referring now to FIG. 5 illustrating in longitudinal section an inner vibrator, this vibrator has a housing mantle 28,which at the ends is closed by a head 29 and a connecting member 30 for the outer mantle 31 of a coaxial hose for supplying or withdrawing air. Compressed air is conveyed to the vibrator through the inner hose 32 of the coaxial hose. The air leaves the vibrator through the annular chamber between the inner hose 32 and the outer mantle 31 of the coaxial hose as is indicated by the arrows 33 and 34. Into the housing mantle 28 of circular cross section, there has been worked a rolling path 35 for the eccentric mass 36. This rolling path is curved in conformity with the curvature of the ball 36 so that the latter will roll on said rolling path while contacting the same along a line. The ball receiving chamber 37 is laterally confined by mantle inserts 38 and 39 which are somewhat spaced from the eccentric mass-ball 36 so that said ball will during its rolling action on track or path 35 not drag on said inserts 38, 39. The inserts 38 and 39 always hold the eccentric mass-ball 36 in the vicinity of the rolling path 35 so that the ball will immediately center on said rolling path when it is acted upon by compressed air.

The compressed air is conveyed to the eccentric mass-ball 36 through a central bore 40 in the insert 39,

a radial passage 41 extends through the insert 39 up to the housing mantle 28, and a longitudinal passage 42 into which leads the radial passage 41. The end member 43 of passage 42, which end member is adjacent to the ball 36, leads substantially tangentially with regard to the rolling path 35 into the ball receiving chamber 37 in order to convey an air flow to the eccentric mass-ball 36 which air flow hits the eccentric massball 36 substantially tangentially with regard to the circulatory path of said ball.

Built into the central bore 40 in the insert 39 is a sliding piston or valve spool 44 which in the position shown in the drawing engages a bore insert 45 that prevents the movement of said valve spool or control piston 44 downwardly t0 the eccentric mass ball 36, said bore insert 45 being fixedly located in bore 40. That end of the bore insert 45 which faces toward the eccentric massball 36 is stepped or offset at its diameter so that between the wall of the bore 40 and the bore insert 45 there is provided an annular passage 46 from which branches off a radial passage 47 that leads into an axial passage 48. This passage 48 is worked into the insert 39 located opposite passage 42 and leads into the annular chamber 49 between the housing mantle 28 and the inner hose 32. The inner hose 32 is in open communication with the annular chamber between the inner hose 32 and the outer mantle 31 of the coaxial hose. The compressed air which acts upon the eccentric mass-ball 36 out of the passage 43 can thus escape to the coaxial hose from the ball receiving chamber 37 through the passages 46, 47 and 48. The sliding piston or valve spool 44 has hollow chamber 53 which is open to that portion of bore 40 which receives the fluid. From hollow chamber 53, a central axially directed bore 51 leads to the lower end face of the valve spool 44 which in this way connects the end faces thereof but in FIG. 5 position of valve spool 44 is closed by a control mass 52. The control mass 52 is in the form of a ball which under the onflow pressure from the inner hose 32 in a rest or detained position, is located in the circular mouth of bore 51 in hollow chamber 53.

On that side of the valve spool 44 which is adjacent to the bore insert 45, there is provided a hollow chamber 55 which is open toward the valve spool 44. Between the bottom of chamber 55 and the lower end face of valve spool 44, there is provided a spring 54 resting thereon. Spring 54 continuously urges valve spool 44 to move upwardly against the pressure acting from the inner hose 32 onto the upper end face of said valve spool 44.

In the closing position of the control mass-ball 52, the upper effective end face of the control piston 44 equals the cross-sectional surface of the bore 40. Spring 54 is so dimensioned that the mass force exerted thereby upon the lower end face of the valve spool 44 is less than the product of the cross-sectional surface of bore 40 times the connecting pressure prevailing in the inner hose 32. In view thereof, and due to the fact that the hollow chamber 35 in the bore insert 45 is vented through a throttling passage 55 toward the compressed air discharge passage 46, in other words, since no material pressure acts upon the lower end face of the valve spool 44, when the control mass-ball 52 is in its closing position, the valve spool 44 will be pressed into the position shown in FIG. 5 in which it engages the bore insert 45.

if, however, the control mass 52 springs out of its rest or retained position shown in the drawing and thereby frees the central bore 51 in the valve spool 44, it will be appreciated that the full connecting pressure can build up on the lower end face of the valve spool 44. This full connecting pressure also acts upon the upper end face of valve spool 44, and this buildup of pressure in the hollow chamber 35 is not interfered with by the throttling passage 55 in view of the narrow cross section of the latter. After both sides of the valve spool 44 are acted upon by the same pressure, spring 53 will be able to displace the valve spool 44 upwardly so that the latter completely closes the radial passage 41. Simultaneously with the closure of the passage 41, a passage 56 behind the upwardly moving lower end face of valve spool 44 is freed. This passage 56 establishes communication of the bore 40 with the axial passage 42 but has a narrower cross section than the passage 41. Inasmuch as a control mass-ball 52 with the here described control operation and control condition does not occupy its rest or retained position so that the bore 51 is open, it will be appreciated that now compressed air can pass from the inner hose 32 through bore 51 and throttling passage 55 into the axial passage 42 and from there to the eccentric mass-ball 36. In view of the throttling effected in the passage 55, however, the quantity of the compressed air flowing onto the ball 36 is considerably less than before when the passage 41 was open.

In view of the above described function of the individual control elements, the inner vibrator of FIG. operates as follows:

It may be assumed that the inner hose 32 is under pressure and that the control mass-ball 52 occupies its rest position shown in the drawing while the inner vibrator is immersed into a mass to be compacted. The supply of compressed air to the eccentric mahs-ball 36 is then efected at a large cross section through the passage 41 whereby the ball rotates in the housing mantle 28 at the working speed and oscillates the inner vibrator to the extent necessary for a compacting action. Inasmuch as the inner vibrator is located in the mass to be compacted, this mass limits the oscillation amplitude of the vibrator to the value provided for the compacting action. Also the control mass-ball 36 oscillates with this amplitude while the arrangement is such that the ball 36 is at this oscillation amplitude safely held in its resting seat by the connecting pressure acting thereupon from the inner hose 32. The mass forces acting upon the oscillation amplitude thus do not suffice to overcome the retaining or resting force.

When after completion of the compacting operation, the inner vibrator is pulled out of the compacted medium, it undergoes a relief with inherent decrease in the running resistance for the eccentric mass-ball 36 and also has its oscillation amplitude increased. In view of l only a slight increase in the speed of rotation of the eccentric mass-ball 36 whereby the valve spool 44 blocks in the above described manner the passage 41 and simultaneously frees the passage 56 through which fluid pressure then acts upon the eccentric mass-ball 36 at a considerably less pressure than previously through passage 4i. As a result thereof, the speed of the ball 36 drops, but in view of the freeing of the inner vibrator,-

its oscillation amplitude remains at a value which will not make it possible for the control mass-ball 52 to return to its rest position. The eccentric mass-ball 36 will then at reduced compressed air supply continue running at its idling speed which, by a corresponding dimensioning of the throttling in passage 51, is preferably below the working speed but exceeds the working speed at any rate by far not to any material extent as is the case with constant compressed air supply through passage 41.

If now the inner vibrator is again immersed into a medium to be compacted, it will be appreciated that due to the renewed confinement of the vibrator and the thus inherent increase in the air resistance for the eccentric mass-ball 36 at the first still throttled compressed air supply through passage 56, the speed of the eccentric mass-ball 36 will still greatly drop until also the oscillation amplitude of this vibrator drops to a very low value below the value of the working speed. This strong drop in the oscillation amplitude also brings about a very considerable decrease in the mass forces acting upon the ball 52 so that ball 52 can now again return to its rest position whereby the valve spool 44' is again moved into the position shown in the drawing until it abuts the bore insert 45,. In this connection, the

passage 41 of large cross section is opened so that for action upon the ball 36 there will now be available the full compressed air'output provided for the compacting operation. The speed of the eccentric mass-ball 36 now increases to the predetermined working speed which the ball 36 maintains until the vibrator is again pulled out of the medium to be compacted whereupon the above described changeover to idling operation take place.

As will be evident from the above, the essential advantage of the method and the vibrator according to the present invention consists in that the operator no longer has to devote his attention to the speed of the eccentric mass and no longer has manually to control the supply of pressure medium in order on one hand to prevent the speed of the eccentric mass from reaching undesired high values during idling operation. On the other hand, the proper speed of the eccentric mass is assured during the compacting operation, and the automatic control of the speed of the eccentric mass reliably saves considerable quantities of pressure medium during the working intervals between the compacting operations. During the idling of the vibrator, a minimum of pressure medium is used, and only when the vibrator is placed under load will the consumption of the pressure medium rise to the value necessary for the compacting operation. The speed of the eccentric mass will also during idling operation safely be relatively low so that the occurring surface pressure will remain below admissible limits. This in turn results in a long life of the parts of the vibrator. The low speed during idling operation also maintains the noise development in tolerable limits so that the surrounding is protected against influences which may be harmful. Low speeds are important with regard to noise development particularly during idling because the vibrator when under load is in contact with the medium to be compacted which in its turn has a necessary damping effect.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawings, but also comprises any modifications within the scope of the appended claims.

What is claimed is:

l. The method of compacting material such as concrete, and the like, which comprises: providing an element for engagement with the material to be compacted, engaging the element by a mass movable in a variable diameter rotary path by fluid pressure and which will develop an eccentric load on the element and vibrate the element when the mass is actuated, supplying fluid under pressure to the mass to actuate the mass in the rotary path of movement thereof, and controlling the said supply of fluid to the mass in conformity with changes in the amplitude of the path of said mass.

2. The method according to claim 1 in which the control of said supply of fluid to said mass is effected in a manner to maintain the speed of said mass substantially constant while said element engages said material and is thus under load.

3. The method according to claim 2 in which the control of said supply of fluid to said mass is effected in a manner to maintain the speed of said mass substantially at the same time constant speed when said element is disengaged from said material and is thus under no load.

4. The method according to claim 2 in which the control of said supply of fluid to said mass is effected in a manner that the speed of said mass is reduced when said element is disengaged from said material and is thus under no load.

5. In a vibrator for compacting materials such as concrete and the like: a housing, an eccentric mass in the housing, a chamber in the housing larger than said mass in which the mass is located and in which the mass is moveable in a circular path to develop an eccentric load on said housing to cause vibration thereof, said housing at one end being engageable with the material to be compacted to impart said vibration thereto, a passage in said housing leading to said chamber and discharging substantially tangentially into said chamber for the supply of fluid under pressure to said mass to actuate said mass to move in said circular path, an exhaust conduit leading from said chamber, control means in said passage for controlling the rate of fluid flow therein, and means responsive to variations in the amplitude of movement of said mass in said chamber for adjusting said control means to control the supply of fluid to said mass.

6. A vibrator according to claim 5 in which said mass is a ball.

7. A vibrator according to claim 6 in which said chamber in which the ball moves in a circular path comprises: a first axial stationary portion fixed in said housing on one side of the ball, and a second axial portion in the housing on the other side of the ball and axially moveable in the housing, means urging said second portion toward the ball, said second portion being operable when moved axially in the housing by the ball to actuate said control means.

8. A vibrator according to claim 7 in which said moveable second portion is cone shaped with the larger diameter end portion facing the said first stationary portion.

9. A vibrator according to claim 8 in which said control means includes a sleeve in the housing movable axially therein, said sleeve being fixed to said second moveable portion so as to move therewith, said sleeve and said housing cooperatively forming a valve in said passage which varies in conformity with movement of said sleeve in said housing.

10. A vibrator according to claim 5 in which said chamber comprises opposed axial portions on opposite sides of said ball each tapering outwardly toward the ball and a peripheral portion extending axially between said axial portions and tapering outwardly in a direction toward said control means.

11. A vibrator according to claim 10 in which said control means comprises a valve piston having one end adjacent the path of said mass, the other end of said valve piston controlling said passage.

12. A vibrator according to claim 11 in which said valve piston has opposed areas of different size therein, the larger of said areas being exposed to the incoming fluid supply, the smaller of said areas being connected to receive fluid from said supply and having restricted communication with said passage downstream from said control means.

13. A vibrator according to claim 10 in which said peripheral portion of said chamber is conical.

14. A vibrator according to claim 10 in which said peripheral portion of said chamber comprises axial portions having respective degrees of taper.

15. A vibrator according to claim 5 in which said control means includes a control mass separate from said eccentric mass and moveable for controlling the rate of fluid supply to said eccentric mass.

16. A vibrator according to claim 15 in which said control mass has a normal position on the axis of said housing and is displaceable radially therefrom under the influence of vibration of said housing.

17. A vibrator according to claim 15 in which said control mass is normally in a radially centered position in said housing and is held therein by the pressure of the fluid in said passage, said control mass being moveable radially away from said position in response to a predetermined amplitude of vibration of said housing, said control mass when in said predetermined radial position permitting maximum rate of fluid flow to said chamber and when displaced radially from said position causing the rate of fluid flow to said chamber to reduce, said control mass returning to said radially centercd position in said housing in response to reduction in the amplitude of vibration of said housing.

18. A vibrator according to 'claim 17 which includes an unrestricted channel leading from said passage to said chamber and a restricted channel leading from said passage to said chamber, a valve member having first and second positions, a respective channel being open and the other closed in each position of said valve member, and means for actuating said valve member in response to movement of said control mass out of and into the said radially centered position thereof.

19. A'vibrator according to claim 18 in which said means for actuating said valve member includes a conduit extending axially therethrough, said control mass closing said conduit in the said radially centered position thereof and releasing said conduit when moved radially away from said centered position.

20. A vibrator according to claim 19 in which said valve member has opposite ends of equal area, one said said control mass is in centered position and opens said restricted channel when said control mass is displaced radially from said centered position.

23. A vibrator according to claim 20 in which said valve member is on the axis of said housing and is moveable axially in said housing, said conduit in said valve member being on the central axis thereof, said valve member having a recess on the said one end receiving said control mass, said control mass being a ball, and the bottom of said recess being conical.

24. A vibrator according to claim 15 in which said chamber comprises a peripheral wall formed on the inside of said housing andfo'rming the path for said eccentric mass, said eccentric mass rollingly engaging said path.

25. A vibrator according to claim 24 in which saideccentric mass is a ball. 

1. The method of compacting material such as concrete, and the like, which comprises: providing an element for engagement with the material to be compacted, engaging the element by a mass movable in a variable diameter rotary path by fluid pressure and which will develop an eccentric load on the element and vibrate the element when the mass is actuated, supplying fluid under pressure to the mass to actuate the mass in the rotary path of movement thereof, and controlling the said supply of fluid to the mass in conformity with changes in the amplitude of the path of said mass.
 2. The method according to claim 1 in which the control of said supply of fluid to said mass is effected in a manner to maintain the speed of said mass substantially constant while said element engages said material and is thus under load.
 3. The method according to claim 2 in which the control of said supply of fluid to said mass is effected in a manner to maintain the speed of said mass substantially at the same time constant speed when said element is disengaged from said material and is thus under no load.
 4. The method according to claim 2 in which the control of said supply of fluid to said mass is effected in a manner that the speed of said mass is reduced when said element is disengaged from said material and is thus under no load.
 5. In a vibrator for compacting materials such as concrete and the like: a housing, an eccentric mass in the housing, a chamber in the housing larger than said mass in which the mass is located and in which the mass is moveable in a circular path to develop an eccentric load on said housing to cause vibration thereof, said housing at one end being engageable with the material to be compacted to impart said vibration thereto, a passage in said housing leading to said chamber and discharging substantially tangentially into said chamber for the supply of fluid under pressure to said mass to actuate said mass to move in said circular path, an exhaust conduit leading from said chamber, control means in said passage for controlling the rate of fluid flow therein, and means responsive to variations in the amplitude of movement of said mass in said chamber for adjusting said control means to control the supply of fluid to said mass.
 6. A vibrator according to claim 5 in which said mass is a ball.
 7. A vibrator according to claim 6 in which said chamber in which the ball moves in a circular path comprises: a first axial stationary portion fixed in said housing on one side of the ball, and a second axial portion in the housing on the other side of the ball and axially moveable in the housing, means urging said second portion toward the ball, said second portion being operable when moved axially in the housing by the ball to actuate said control means.
 8. A vibrator according to claim 7 in which said moveable second portion is cone shaped with the larger diameter end portion facing the said first stationary portion.
 9. A vibrator according to claim 8 in which said control means includes a sleeve in the housing movable axially therein, said sleeve being fixed to said second moveable portion so as to move therewith, said sleeve and said housing cooperatively forming a valve in said passage which varies in conformity with movement of said sleeve in said housing.
 10. A vibrator according to claim 5 in which said chamber comprises opposed axial portions on opposite sides of said ball each tapering outwardly toward the ball and a peripheral portion extending axially between said axial portions and tapering outwardly in a direction toward said control means.
 11. A vibrator according to claim 10 in which said control means comprises a valve piston having one end adjacent the path of said mass, the other end of said valve piston controlling said passage.
 12. A vibrator according to claim 11 in which said valve piston has opposed areas of differeNt size therein, the larger of said areas being exposed to the incoming fluid supply, the smaller of said areas being connected to receive fluid from said supply and having restricted communication with said passage downstream from said control means.
 13. A vibrator according to claim 10 in which said peripheral portion of said chamber is conical.
 14. A vibrator according to claim 10 in which said peripheral portion of said chamber comprises axial portions having respective degrees of taper.
 15. A vibrator according to claim 5 in which said control means includes a control mass separate from said eccentric mass and moveable for controlling the rate of fluid supply to said eccentric mass.
 16. A vibrator according to claim 15 in which said control mass has a normal position on the axis of said housing and is displaceable radially therefrom under the influence of vibration of said housing.
 17. A vibrator according to claim 15 in which said control mass is normally in a radially centered position in said housing and is held therein by the pressure of the fluid in said passage, said control mass being moveable radially away from said position in response to a predetermined amplitude of vibration of said housing, said control mass when in said predetermined radial position permitting maximum rate of fluid flow to said chamber and when displaced radially from said position causing the rate of fluid flow to said chamber to reduce, said control mass returning to said radially centered position in said housing in response to reduction in the amplitude of vibration of said housing.
 18. A vibrator according to claim 17 which includes an unrestricted channel leading from said passage to said chamber and a restricted channel leading from said passage to said chamber, a valve member having first and second positions, a respective channel being open and the other closed in each position of said valve member, and means for actuating said valve member in response to movement of said control mass out of and into the said radially centered position thereof.
 19. A vibrator according to claim 18 in which said means for actuating said valve member includes a conduit extending axially therethrough, said control mass closing said conduit in the said radially centered position thereof and releasing said conduit when moved radially away from said centered position.
 20. A vibrator according to claim 19 in which said valve member has opposite ends of equal area, one said end being exposed to fluid pressure in said passage, said conduit connecting said ends of said valve member, a cavity at the other end of said valve member into which said conduit opens, and a spring in said cavity urging said valve member toward said one end thereof.
 21. A vibrator according to claim 20 which includes a restricted passage connecting said cavity with said exhaust conduit.
 22. A vibrator according to claim 21 in which said valve member opens said unrestricted channel when said control mass is in centered position and opens said restricted channel when said control mass is displaced radially from said centered position.
 23. A vibrator according to claim 20 in which said valve member is on the axis of said housing and is moveable axially in said housing, said conduit in said valve member being on the central axis thereof, said valve member having a recess on the said one end receiving said control mass, said control mass being a ball, and the bottom of said recess being conical.
 24. A vibrator according to claim 15 in which said chamber comprises a peripheral wall formed on the inside of said housing and forming the path for said eccentric mass, said eccentric mass rollingly engaging said path.
 25. A vibrator according to claim 24 in which said eccentric mass is a ball. 